Occurrence in mammalian liver of a protein which replaces the B protein of E. coli quinolinate synthetase. |
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Authors: | S Sakakibara F D Wicks R K Gholson |
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Institution: | Department of Biochemistry, Agricultural Experiment Station, Oklahoma State University, Stillwater, Oklahoma 74074 USA |
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Abstract: | contains two proteins (A and B) which together convert dihydroxyacetone phosphate and aspartate to quinolinic acid, a precursor of NAD. Although mammalian liver homogenate does not catalyze this reaction it contains a protein which will replace the B protein of the system. The behavior of the liver protein on Sephadex G-75 suggests it is much smaller than the B protein. Liver B protein also appears to contain tightly bound FAD while FAD is easily removed from the B protein. The pH optimum for the hybrid system A protein-liver B protein is 9.0 while in the pure system the optimum is pH 8.0. The hybrid system is inhibited by NAD to the same extent as the pure system. |
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